A fuel tank having an internally mounted wave-damping member made of a fibrous resin material is known, as disclosed in Japanese Patent Application Laid-Open Publication No. HEI-05-139169 (JP 05-139169 A).
With the aforementioned wave-damping member, however, the tank body is bisected into an upper and a lower portion, and the member cannot be used in a single-piece fuel tank. Specifically, a wave-damping member made of a resin material is sandwiched and held in place between the edge of an upper shell above and the edge of a lower shell below in the fuel tank, but the problem is that because a resin tank is usually manufactured by hollow molding (blow molding), the wave-damping member cannot be installed inside the resin-tank body.
Using a wave-damping member in a resin-tank body brings about a problem in that limitations in terms of the shape of the wave-damping member, the size of the wave-damping member, the mounting location, and the like become more stringent with the insertion of the wave-damping member into the tank body. Another problem is that the structure for fixing the wave-damping member in the fuel tank becomes more complicated.
Also known is a fuel tank in which a blowhole is used during molding of the resin-tank body and in which a tilting shutoff valve or other functional component is mounted in the opening, as disclosed in Japanese Patent No. 3,893,337.
The fuel tank disclosed in Japanese Patent No. 3,893,337 presents a problem in that since a functional component is welded in a hole formed in the tank wall, the barrier layer in that area is adversely affected, and there is a danger that penetration through the weld may occur. Another problem is that the structure for mounting the functional component is complicated.
A resin fuel tank in which a wave-damping plate extends halfway into the tank from the upper wall of the tank, and the remainder of the wave-damping plate extends into the tank from the bottom wall of the tank in order for the wave-damping plate to be placed in the tank in an upright manner is also known, as disclosed in Japanese Utility Model Application Laid-Open Publication No. SHO-57-032909 (JP-U 57-032909 A).
The fuel tank disclosed in JP-U 57-032909 A presents a problem in that because the wave-damping plate extends into the tank, there is a danger that the capacity of the tank will decrease. Another problem is that the degree of freedom in selecting the shape of the wave-damping plate is low, as is the degree of freedom in selecting the mounting location, making it difficult to obtain a significant effect.